1. Field of the Invention
The present invention relates to a system for reading an information code, an apparatus for reading an information code, and a medium on which an information code is formed, and in particular to the system, apparatus and medium directed to an information code with enhanced confidentiality.
2. Related Art
Various kinds of information codes, such as bar codes and two-dimensional codes including QR codes (registered trademark), are now used in various applications. The information codes are formed on (or in) various types of mediums (or objects) such as printed paper sheets and displayed screens, and present pieces of necessary information by encoded codes mapped thereon.
The applications of these codes are now becoming diversified. Among diversifications, there is a growing need for higher security of the information codes. That is, it is strongly demanded that it is possible to read out contents of an information codes only when a specific condition is met. As one of countermeasures for this demand, Japanese Patent Laid-open Publication No. 2010-146461 provides a technique of providing the information code with a security function.
Practically, the technique provided by the foregoing publication is that key information is overlapped and printed on main data by using printing liquid visible only under ultraviolet rays. According to this printing technique, the key information cannot be visible under visible light rays, increasing the security of the code data encoded on a predetermined manner.
However, the printing technique provided by the foregoing publication still has a drawback about an operator's visible viewing of the key information for reliable confirmation. Specifically, by this printing technique, the key information is converted to numerical data and added, and an operator is requested to visibly view the numerical data under ultraviolet rays. The drawback is that whether or not the operator is able to visibly view the key information reliably largely depends on environments (such as printing environments and reading environments) and configurations of a code (such as a code size and how the key information is configured).
Especially when the information code is desired to be compact in size, there often occurs a situation where an operator cannot visibly view the key information though a reader can read the encoded code data itself. In such a case, the operator cannot obtain the key information, failing in decoding the encoded code data. In addition, the operator should read the code data and the key information overlapped on one the other, whether the information code can finally be read successfully depends on experience of the operator. This makes it difficult to read the information code in a quick and reliable manner.